Many high school students get part-time jobs to help pay for expenses or start saving for college. In her book Make Your Kid a Money Genius, author Beth Kobliner suggests students shouldn’t work more than 15 hours a week, though, citing a University of Michigan study.

Researchers from the University of Michigan studied groups of middle school and high school students for 8-12 years to see how senior year employment affected them in the long term. They found a link between college completion and a heavy workload. A press release for the study reported:

By age 29 or 30, more than half of the high school graduates who had worked 1-15 hours a week when they were in 12th grade had completed a bachelor’s degree; but every additional 5 hours of work was associated with an 8 percentage point drop in completion, so that only about 20 percent of those who had worked 31 hours or more finished college. After statistical controls for other prior factors, rates of college completion for those who worked 1-15 hours were still one and a half times the rates for those who worked 31 or more hours.

The study’s lead author said that students who did best didn’t work more than 15 hours a week on average. Of course, mileage will vary: some students may be able to handle a heavier workload and that might be way too much for others. For more detail, check out the links below.